The suspension of a vehicle such as an automobile includes a pressure damper utilizing a damping force generation mechanism to appropriately alleviate vibration transmitted to the vehicle body from a ground surface during travel so as to improve riding comfort and handling stability. The pressure damper includes, for example, a defining member, a rod member, and a damping force generation member. The defining member is movably disposed in a cylinder to define the inside of the cylinder. The rod member is coupled to the defining member. The damping force generation member is disposed in the cylinder to resist against a flow of fluid in accordance with a displacement of the defining member so as to generate damping force. In the pressure damper, damping force is generated by the defining member in accordance with each displacement of the rod member in one direction and in the other direction.
As illustrated in FIG. 44, a patent publication discloses a conventional technique in which a damper is defined into a lower chamber 94A and a reservoir chamber 94B by a piston 93 disposed in an end portion of a cylinder 91. The piston 93 includes a communication hole 931 and a valve 95. The communication hole 931 is formed in a base 932 of the piston 93 to allow the lower chamber 94A and the reservoir chamber 94B to communicate with each other. The valve 95 allows the communication hole 931 to be open and closed to provide damping force. A press member 96 opposed to the valve 95 is displaced to press the valve 95 against the base 932 so as to change the set load of the valve 95. Thus, the damping force in the damper is changed (see patent document 1).